It's August in Florida.. of course it's going to rain. The difference is that it is rarely a long rain. Usually just a passing storm. Don't let this weather get you down. Bring or buy ponchos and just forge ahead. It's what you make of it.
First off have a plan. For my group we bring movies and have cards in our owner's locker just in case the weather got that bad... which it never has. If it rains just keep on keeping on. The rain will stop... and the good news is the parks clear out. So be patient and it will be worth it. I don't suggest doing the norm, like Disney Quest, everyone out there has the same idea. You can always resort hop. See the different resorts. Something you wouldn't do if the weather was awesome for the entire trip. My biggest suggestion is try not just to take the bad about the weather. You are going to the greatest place of earth.
By the way..... this time next week EPCOT to see Spaceship Earth before it goes down for the rest of our trip.